Highly invasive red fire ants could soon be setting up home in Britain thanks to global warming, a pest expert has warned. The creature may only be the size of a grain of rice but their bites can be so painful they require medical treatment and can ­trigger fatal allergic reactions.

As pests go they are known for being destructive and are one of the costliest to deal with. Although none have yet been found in the UK, Gerwyn Jones, president of the Pest Management Association of New Zealand, warned it is only a matter of time. If they became established Mr Jones ­estimates it would cost £500million annually to try to eradicate them, while they rack up a potential death toll of 30 people a year.

In less than a century the insects have spread from their native South America into Mexico, the US, Australia, New Zealand, China and Taiwan. Two years ago, they were found in southern Europe for the first time and modelling suggested 7% of Europe was suitable for the ants, mostly in agricultural land and in urban areas such as London and Paris.

But by 2050, the model predicted most of southern and western England could be at risk, while Belgium and the Netherlands would be ideal breeding grounds. Mr Jones said Australia’s battle with the ants, where annually 570,000 people need medical treatment for stings, should serve as a warning for the UK and other countries currently free of them.

He said: “Their aggressive swarming behaviour poses serious threats to both humans and animals, particularly small pets and wildlife that cannot escape quickly enough.” Their small size allows them to “hitch rides” on imported goods, including plants, soil, construction materials and ­packaging, and once established they can rapidly expand their territory, constructing massive underground colonies that can house hundreds of thousands of ants.

They also threaten farming and wildlife, driving some native species to extinction. He said: “The UK, with its extensive trade networks, is particularly ­vulnerable to accidental introductions of fire ants. The UK’s relatively cooler climate previously provided natural protection but with warming trends accelerating, this advantage is rapidly diminishing.” Mr Jones called for tighter biosecurity at ports, early detection systems and effective control plans. 

He said: “By acting swiftly and decisively, the UK can avoid becoming the next battleground in the fight against these tiny yet ­formidable pests.”

At present, the European fire ant is one of the few ant species in the UK that can sting. It is similar to a wasp sting but not as severe, though multiple stings can be painful, especially for children or pets.

A Defra spokesperson said: “This Government will never waver in its duty to protect the UK’s biosecurity, nature and the economy. We are not complacent and keep a close watch for future threats and take action where necessary.”